Apparatus for the liquefaction and separation of the constituents of gaseous mixtures



Oct. 26, 1926.

- Lfi4248 C. C. VAN NUYS APPARATUS FOR THE LIQUEFACTION AND SEPARATION OF THE CONSTITUENTS OF GASEOUS MIXTURES o i i Filed Sept. 9, 1920 INVENTOR BY Qiw M v M A, ATIOFNEYJ Patented Oct. 26,1926. J UNITED "STATES 9 1604,2418; PATENT OFFICE.

CLAUDE C. VAN NUYS, OF CRANFORD, NEW JERSEY, ASSIGNOR TO AIR REDUCTION COMPANY, INCORPORATED, OF YORK, N. Y., A CORPORATION OF NEW YORK.

APPARATUS non THE n'IQUnrA'c'rIon AND SEPARATION or run oonsrrrunn'rs oi? GASEOUS MIXTURES.

Gn'ginal application' filed september'e, 1920, Serial No. 409,197. Divided'an d'this application filed December 6, 1924.

This invention relates to the liquefaction.

110 tion and auto-purification by a backward re turn of the liquidin contact with the gas has been advantageouslyemployed to produce a liquid enriched. in a less volatile constituent of the mixture, which liquid is subsequently subjected to rectification to separate the more volatile constituent. lln such a method, the liquid originally formed should have a composition approximately in phase equilibr um with the gaseous mixture which is to be W treated. It has been foxund, however, that a -simple liquefaction with backward return does not permit of suficient separation of the gaseous constituents to insure a liquid having the composition desired to attain the W highest efficiency. lhus, in the separation of oxygen from nitrogen in the atmosphere, the liquid formed should contain approximately 47% oxygen, but it hasbeen impossible heretofore to produce such aliquid, be-

M cause as has been discovered, the volume ,of liquid returning and particularly at the lower ends ofthe condensing tubes is such and its rate of travel isso high that no opportunity is afiorded for the desired sepaw ration. In a well-known method employing this principlev of condensation with backward return,'ther e is, in addition to the dificulty just mentioned, the further disadvantage that, the enrichment in the less volatile constituent obtained b backward return is reduced by the ad it ion to the liquid delivered bythe backward return condenser ofa certain amount of unenriche'd liquid air in order to make up losses of liquid due to heat leakage. Since the liquid is delivered to a rectifier inwhich'the final sepa ration of the constituents is accomplished 5 vin contact wlth further portlons of the air and governs more or less the composition of the eflluent gas, it will be appreciatedthat '5 the provision of an'initial' liquid of the de-' sired composition is of the highest importance in the successful and eflicient recovery of constituents of gaseous mixtures) Serial N 0. 754,280.

The object of the present invention is, therefore, to provide an apparatus for separating the constituents of gaseous mixtures in whichan initial liquid is produced having substantially the theoretically possible composition ofthe liquid in phase equilibrium with the incoming air.

Further objects and advantages of the in vention will be apparent as it is better understood by reference to the following speci fication when read in connection with the accompanying drawing which diagrammaticalbe ly illustrates an apparatus adapted to' the accomplishment of the desired object.

lt is to be understood that while the apparatus illustrated is that preferably. employed in carrying out the invention, various re modifications may be introduced and no at.- tempt has been made to illustrate details which may be readily supplied by those skilled in the art. Furthermore, while the invention will be described more particular-' at 1y with reference to the separation of oxygen and nitrogen from air, the apparatus is ap plicable to the treatment of gaseous mixtures in general and no limitation is implied,

therefore, by reference to the atmosphere and at the constituents thereof. In describin the apparatus the atmosphere will be consi ered as comprising oxygen and nitrogen, thereby disregarding the rare elements present, sincethese elementsdo not materially aifect the as operation so far as the production of commercialo gasesis concerned.

In carrying out the invention, air is delivered, after it has been compressed and v cooled in the usualma nner, to an apparatus in which'it is subjected 'to indirect contact with colder liquid and gaseous products, the liquids being held at "somewhat lower pressures so that they are permitted to evaporate through transfer of heat from the incomin air. A portion of the air is thus liquefied and this portion consisting of substantially all of'the oxygen'with some ofthe nitrogen flows backwardly within tubes provided in the apparatus, as hereinafter described,

ascendin in the tubes, and tends durin its, backward passage .to become 'enriche i'n oxygen while a portion of the nitrogen is. taken up and carried away with the residual unliquefied portion of the air. This're sidual gas is substantially pure nitrogen and in the preferred embodiment of my invent1on the mtrogen is withdrawn and may be applied to any desired purpose after its cold has been transferred to incoming air. The

nitrogen, being delivered at the initial presdesired composition may be accumulated.

The liquid escaping from the tubes in which it is formed is, for the purpose of the present invention, permitted to tell u on trays where itis subjected in relatively t in layers to the action of the incoming air for the urpose of carryin out a. partial rectificatlon by contact of t e air therewith and consequent separation of the more volatile constituent, nltrogen, while oxygen from the air is liquefied and remains with the liquid.

This li uid in passing over the trays isgradua y enriched in oxygen and finally accumulates in a body which approximates a composition in phase equilibrium with the incoming air and contains, therefore, substantially 47 per cent of oxygen, the remainder being nitrogen.

Liquid accumulated in this manner is delivered through a reducing valve to'a rectifier where it is subjected to direct contact with vapors arising from the liquid evaporated by the initial condensation of the air. By this means the constituents are se arated, the oxygen accumulating in the liquid while nitrogen and a portion of the oxygen is released and the two gases escape as an efliuent having a composition in phase equilibrium with the liquid delivered to the rectifier. Since this liquid is materially enriched in oxygen, the liquid which finally accumulates as a result of the rectification will be correspondingly richer in oxygen and the gaseous oxygen roduced by evaporation thereof will beef t e highest quahty and adapted to the most refined uses. The liquid oxygen which accumulates in the apparatus and is there vaporized is delivered in an extremely cold condition, and the pressure at which air enters the cycle may be high enough so that the oxy on is still at a relatively high pres- .sure, alt ough the original pressure is somewhat reduced by the passage of the-liquid through the reducing valve. After giving up its cold to the incoming air, the oxygen may, it at a relatively'high pressure, be exin the refrigeration and to recover a portion of the energy which was initially used in compressing the air.

Obviously while the particular feature of rectification to produce a liquid initially rich in oxygen is described herein in connection with numerous details of a method to which it is particularly adapted, it may be employed in connectionv with other methods requiring the delivery of a liquid mixture to a rectifier.

Referring to the drawing for the more particular features of the invention, 5 indicates a column having a pot 6, a preliminary rectifier-7, a gas chamber 8, a liquid chamber 9 in which a receptacle 10 for liquid-is suspended, and a rectifyin compartment 11.

Cold compressed air is delivered to the pot 6 through a pipe 12 and passes thence through trays 13 upon which the liquid fraction of the compressed air accumulates. The air thence passes through tubes 14 in indirect. contact with cold gaseous products of the operation in the chamber 8 and with liquid in the chamber 9 and receptacle 10 which cools the air to such an extent that substantially all of the oxygen and some of the nitrogen are liquefied. The tubes 14 terminate in a head 15 from Which'the residual gas consisting substantially of nitrogen is delivered through a pipe 21.

During its passage backwardly through the tubes in contact with the air, the liquefied fraction of the lair is subjected to autopurification, the air aking up nitrogen from the liquid and supplying oxygen thereto so that the liquid is gradually enriched in v oxygen until it is delivered to the trays 13. Here enrichment in oxygen is augmented by the action of the incoming air which drives off a considerable proportion of the remaining nitrogen from the liquid while oxygen from the air is liquefied therefrom and joins the liquid which flows into the pot 6. This liquid accumulating in the pot has a composition which is substantially in phase equilibrium with the incoming air, the proportion of oxygen being substantially 47 per cent,'the maximum theoretical composition which is obtainable under the conditions prevailing.

- From the pot 6 the liquid is delivered through a pipe 17 and reducing valve 18 'to therectifying compartment 11 where it flows downwardly over trays 19 and is subjected therein to the action ofvapors arising from the chamber 9 as a result of vaporization of the liquid by indirect contact with the air within the tubes 14. The more volatile constituent,'nitrogen, is thereby vaporized while the liquid becomes more and more enriched in oxygen, being finally delivered'through flows into the cham er 9. The liquid accupanded in suitable engines in order to assist mulating in the chamber 9 is substantially pipe 22.

compartments D and C connected by a pipe,

the bafiles 23 and around the tubes.

To provide for heat interchange between the incoming air and the gas leaving the apparatus, an exchanger is employed comprising a plurality of sections A, B, C and D which are substantially identical in form, being provided with baflies 23 and sets of tubes 24 and 25 which communicate with compartments v26, 27, 28 and 29 for the purpose of conveying the gases in indirect contact with the incoming air circulating abolut Tie sections of the exchanger are connected by pipes 30, 31 and 32 so that the air entering the exchanger is permitted to pass through the sections successively and is finally delivered through the pipe 12 to the column.

Nitrogen delivered by the pipe 21 from the column enters the compartment .26. of the section I) and travels successively through 33. l The nitrogen is withdrawn from the compartment 26 at the end of the section 0 .fles 38 therein and about the .tubes14 for the purposes hcreinbe'fore described. Escaping from the chamber 8 the gas is delivered through a pipe 39 to the compartment-27 at i the end of the section D of the exchanger and passes through the tubes 25 of the several sections of the exchanger to the compartment 27. at'the'endof section A from which it escapes through a pipe 40' controlled by a valve 41.

' The remaining nitrogen is conveyed through. a pipe 42 to the compartment 26- in section B of the exchanger and passes through the tubes 24 in' sections A and B which are connected by a' pipe/43. .The nitrogen is delivered to the compartment 26 at the end of the section A of the exchanger and is conveyed through a pipe 44 controlled by a valve 45 to 'an expansion engine 46 where the nitrogen is expanded and thereby cooled. The cooled nitrogen is conveyed from the engine by a pipe 47 and a portion thereof'is delivered through a pipe-48 to the compartment 27 of the section B of the exchanger where it joins the previously 'expanded nitrogen from the engine 36 and is delivered therewith to the outlet 40. An-

other portion of the nitrogen from the engine 46.is conveyed through a pipe 49 controlled bya valve 50 to an exchanger 51 where it serves in passing through the tubes 52-there of to cool the incoming air d zlivered to the exchanger through an intake 53. The nitroconnects the pipe 55 to the pipe 44 so that in starting the apparatus air after compression and passage through the apparatus may be expanded in the engine 46 to produce the necessary refrigerating effect.

The .efliuent gasfrom the column p'as'ses through'the pipe 22 to the compartment 28 at the end of the exchanger and thence travels through tubes 25- in the successive sections'to the compartment 28 at the end of the section A of the exchanger. The efliuent gas is withdrawn through a pipe 59f controlled by a valve 60 and in the normal operation of the apparatus is conveyed through a pipe 61 controlled by'a valve 62' to the inlet pipe 63 of the air compressor 64. The pipe '63 is conneted to the exchanger 51' and receives the air cooled therein for conveyance to the compressor. The air is introduced through a pipe 53. By permitting the eflluent gas from the column to mix with this incoming air, the temperature of the air ma be further reduced before com ression wit corres'onding advantage in t e energy reuire for compression and, moreover, the efuent gas is returned to the cycle so that all of the air initially compressed is eventually separated and the constituents thereof the pipe 12 to a pot 6 at the bottom of the column. To assist in accumulating refrigerative eflect in'commencing the operation, a by-pass 67 connects the pipes 59' and 34 and is controlled by a valve 68. When the valve 68 is open and the valve .62 is closed, the. ,eilluent from the top of the column which in starting consists of air passing through the w ere it is expanded and cooled.

From the foregoing description, it will be apparent that I have introduced a' novel feature with resulting improvement of liquea apparatus, is delivered to the engine 36 faction operations as heretofore conducted. By providing for rectification of the liquid initially formed in the apparatus before it is conveyed to the rectifier, the initial com position of this liquid in oxygen, for example, is markedly improved with the result that a closer and more economical separation is possible in the rectifier.

Various changes may be made in the apparatus disclosed without departing from the invention or sacrificing any ofthe'advantages thereof.

I claim 1. In an apparatus for separating the constituents of a gaseous mixture by liquefaction and rectification, the combination of a column having a compartment for a body of liquid, tubes traversing the compartment, a head in which the tubes terminate,a chamber beneath said compartment and communieating with thetubes, an inlet for the mixture to the chamber, means therein to effect preliminary rectification of the liquid formed in the tubes by contact with the incoming mixture, a rectifier above said compartment and means for delivering liquid from the chamber to said rectifier.

2., In an apparatus for separating the constituents of a" gaseous mixture by liquefaction and rectification, the combination of a column having a compartment for a body of liquid, tubes traversing the compartment, a head in which the tubes terminate, a chamber beneath said compartment and communicating with the tubes, an inlet for the mixture to the chamber, means therein to eifectpreliminary rectification of the liquid formed in the tubes by contact with the incoming mixture, a rectlfier above said com artment, means for delivering liquid from he chamher to said rectifier, means for withdrawing residual unliquefied gas from said head and means for recovering energy from the residual gas.

3. In an apparatus for separating the constituents of a gaseous mixture by liquefaction and rectification, the combination of a column having a compartment for a body of liquid, tubes traversing the compartment, a head in which the tubes terminate, a chamber beneath said compartment and coinmunicating with the tubes, an inlet for the mixture to the chamber, means therein to.

effect preliminary rectification of the liquid formed in the tubes by contact with the incoming mixture, a rectifier above said compartment, means for-delivering liquid from I the chamber to said rectifier, means for withdrawing residual unhquefied gas from said head, means for recovering energy from the residual s, including heat inter-changers wherem t e residual gas is warmed and one or more engines wherein the gas is expanded.

,- 4. In an apparatusfor separating the con of a gaseous mixture by hquefac neonate tion and rectification, the combination of a. column having acompartment for a body of liquid, tubes traversing the compartment, a head in which the tubes terminate, a chamber beneath said compartment and communicating with the tubes, an inlet for the mixture to the chamber, means therein to effect preliminary rectification of the liquid formed in the tubes by contact with the incoming mixture, a rectifier above said compartment, means for delivering liquid from the chamber to said rectifier, and means for withdrawing an efiluent gas from the rectifier and returning it to the chamber.

5. In an apparatus for separating the constituents of a gaseous mixture by liquefaction and rectification, the combination of a column having a compartment fora body of liquid, tubes traversing the compartment, a head in which the tubes terminate, a-chamber beneath the compartment'and communieating with the tubes, means for com ressing and cooling the mixture and for de ivering it to the chamber, means in the chamber to'efiect rectification of the liquid formed in the tubes, a'rectifier above the compartment, means for delivering liquid from the chamber thereto, and means permitting cooling of the gaseous mixture before it enters the compressing means.

6. In an apparatus for separating the constituents of gaseous mixtures, the combination of means for subjecting the gaseous mixture to selective liquefaction and means for subjecting the liquid thus produced to rectification by contact with the incoming gaseous'mixture before the latter is delivered to the selective liquefaction means.

7. In an apparatus for separating the constituents of gaseous mixtures, the combination of means for subjecting the gaseous mixture to selective liquefaction, means for subjecting the liquid thus produced to rectifieation by contact with the incoming gaseous mixture before the latter is delivered to the selective liquefaction means, and means for subjecting the liquid product of the first rectification to a further rectification in contact with vapors from previously rectified portions thereof.

8. In an apparatus for separating the constituents of gaseous mixtures, the combination of means for subjecting the gaseous mixture to selective liquefaction including a plurality of tubes through which the gaseous mixture is permitted to pass and means below the tubes for subjecting the gaseous mixture first to rectification by contact with the liquid produced in the tubes.

9. In an apparatus for separating the constituents of gaseous mixtures, the combination of means for subjecting the gaseous mixture to selective liquefaction includinga plurality of tubes through which thegaseous mixture permitted to pass, means below the tubes for subjecting the gaseous mixture first to rectification by contact with the liquid produced in the tubes, and means for subjecting the liquid product of the first 5 rectification to further rectification in contact with vapors from previously rectified portions thereof.

, 10. In an apparatus for separating the constituents of gaseous mixtures, the combination of means .for subjecting the gaseous mixture to selective liquefaction, means for subjecting the liquid thus produced to rectification by contact with the incoming gaseous mixture before the latteris delivered to the selective liquefaction means, means for subjecting the liquid product of the first rectification to a further rectification in contact with vapors from previously rectified portions thereof, and means for returning LAUDE 0. VA 

